The investigators will in this project make a cohort study in which all RYGB operated patients in the Central Denmark Region and the North Denmark Region during the period 2006 - 2011 (about 5000 patients) will be included and from the combination of the various registers (see research plan) we will be able to estimate e.g. mortality, readmissions in the surgical department (reoperations), length of stay in the surgical department / intensive care unit and the length of patient follow-up in a medical context, referrals and readmissions in medical wards,